someone may have pointed this out already, but possible goof...
In the scene with the knights who say ni. The lead knight says the word that is a weakness to them at least once. During the sequence when they're in agony they make it clear that they can't say the word in addition to hearing it. The word is "it".
They say it once when in the line "it is a good shrubbery" and then earlier King Arthur says the word "it" without the knights freaking out.
Inconsistency? Anyone else notice this? Not that it matters in a movie like this.